This invention relates to novel primer compositions. More particularly, the invention relates to novel primer compositions useful for forming a strong adhesive bond between the substrate and an overlaying room-temperature-curing silicone rubber composition.
In the application and cure of room-temperature-curing silicone rubber compositions to and on substrate, a variety of primers have been used to produce a strong adhesive bond between the cured silicone elastomers and the substrates. The known primers comprise, for example, alkoxy silanes, such as, vinyl trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-methacryloxypropyl trimethoxysilane, and N(2-aminoethoxy)-3-aminopropyl trimethoxysilane, condensates of partial hydrolyzates or cohydrolyzates of these silanes, titanic acid esters, metal salts of fatty acids, or peroxysilanes. Those primers can, advantageously, serve to make room-temperature-curing silicone rubber adhere to an iron or aluminum surface but disadvantageously, they do not so work when the silicone rubber is cured by the crosslinking mechanism of dehydroxylamination reaction. Further the known primers are disadvantaged by the facts that they show little effectiveness to glass, mortar and asbestos surfaces and that the cured silicone rubber adhesively bonded to the substrate of iron or aluminum with these primers tends to readily peel off when affected by water.